The present invention relates to apparatus for stunning and/or killing domestic poultry species electrically. The invention is also applicable to the electrical stunning and killing of ostriches. Although ostriches are not strictly speaking poultry, the term xe2x80x9cpoultryxe2x80x9d as used herein will be taken to include ostriches. In some aspects, the invention relates to the handling and electrical stunning/killing of animals in general. The invention, in all its aspects, is particularly suitable for use with broiler chickens.
Current systems for electrically stunning broiler chickens involve the broiler being suspended by its legs on a moving shackle line. The shackles from which the broilers are suspended are electrically grounded; as the broilers proceed along the line, their heads pass through an electrified water bath, thereby completing the electrical circuit between the shackle and the water bath. An electrical current thus flows through the entire bird from its head to its legs. It is necessary for this current to be maintained for several seconds to achieve an effective stun and, therefore, to achieve an acceptable throughput of broilers, it is necessary that a number of the birds are passing through the water bath at any given time; this number will obviously be somewhat variable.
The above system has several problems, one of which is that, with a variable number of birds completing the electrical circuit between the shackle line and water bath at any one time, the current through any individual bird will vary. This results in some cases in an ineffective stun. In order to solve this problem, a system has been developed whereby a constant current passes through each individual bird irrespective of the number of birds passing through the water bath at any one time. The system is described in co-pending international patent applications numbers WO 97/1283 and WO 97/01284, each assigned to the applicant of the present application.
Whilst the system referred to above is very effective in that it ensures that each bird completes a separate electrical circuit, there are still problems with the water bath method of electrocution. The current passing through each bird can still be unpredictable because the path which the current takes is not always predictable; for example one of the birds"" wings may touch the surface of the water bath providing an additional current path. The systems in use at the moment also require a relatively high voltage, of the order of 200 volts, and it would be desirable if this could be reduced.
At present, in poultry systems at least, electrical methods are generally used only for stunning. The neck of the stunned bird is then cut and the bird dies through exsanguination. This procedure has been followed for a number of reasons, including the fact that there is a generally held view that the amount of blood draining from the bird""s body is increased if the bird""s heart is still beating when the neck is cut. It has been determined through experimentation with poultry that, whilst the initial blood flow rate is higher if the heart is beating when the neck is cut, the amount drained is no different if the heart has stopped beating.
A system is currently in use with pigs which involves applying to the head a voltage sufficient to stun the animal and then applying an electrode to the chest to induce a current through the heart to cause death by fibrillation.
This method would be unsuitable for use with poultry because it may have a negative effect on the quality of the breast meat. This problem does not arise in pigs and other red meat animals where the chest area yields very little meat.
The inventors have found, however, that an electrical stun/kill process can be used with poultry by applying the fibrillating voltage using an electrode placed at the rear of the bird rather than on its chest. It is somewhat unexpected that an electrode in this position would produce a flow of current through the heart, and still more surprising that the electrical resistance offered for example between the rear of the bird and its head would be as low as it has been found to be.
It is postulated that the high electrical conductivity of the spinal cord and viscera is in the main responsible for the low electrical resistance of this current path.
The present invention, in its various aspects as detailed below, has one or more of a number of objectives. These include the minimising, preferably to substantially zero, of the possibility of the bird being conscious when its neck is cut. A further objective, which is at least partly connected to the above objective, is to minimise the electrical resistance in an electrical stun and/or kill process and to make this resistance as consistent as possible. Minimising the voltage means that the electrical safety of the system in case of accidental contact by operators is improved. Low voltage requirements also mean that electrical equipment reliability is likely to be improved. Making the resistance consistent means that the current flowing through the bird for a given applied voltage is made as predictable as possible, with consequent reduction of the possibility of any bird not being effectively stunned and/or killed.
Another objective is to allow the humane stunning and/or killing of animals, especially poultry, in a normal position, ie head uppermost. A system has recently been devised (see EP-A-0584142 ) for restraining and conveying poultry such that the bodies of the birds are substantially localised with respect to the moving conveyor and the orientation of the birds is fixed in a predetermined direction. However, no stun/kill apparatus using this conveyor has yet been devised as far as the inventors are aware. It represents a considerable improvement in welfare terms to avoid suspending birds by their legs before they are rendered unconscious.
Another objective of the invention in one or more of its aspects is to provide apparatus and a method for stunning and killing poultry which avoids excessive wing flapping and other movement of the bird during the process. This has advantages in welfare terms and avoids damage to the carcass. In current known systems, dislocated joints, broken wings and other bones, and damage to edible meat are all problems.
A further objective of the invention is the humane restraint of the head and/or neck of animals, particularly poultry, on a conveyor system, to allow for an electrical stun/kill process to be performed on their heads/necks.
According to a first aspect of the present invention, poultry slaughter apparatus comprises:
(a) a first device for inducing a stunning electrical current to flow through the head of a bird;
(b) a device for applying an electrical voltage between the head and the rear of the bird such that a fatal electrical current passes through the heart of the bird;
(c) restraint means; and
(d) a control system arranged to cause the said first device to commence operating on a given bird restrained by the said restraint means and, simultaneously or subsequently, to cause the said second device to commence operating on the said restrained bird.
It has been found that this apparatus can deliver a slaughtered bird in a short space of time with little or no wing flapping, although the bird may stiffen when the fibrillating current is applied. The slaughtered bird is limp, as compared to conventional systems where the killing stage involving exsanguination, induces xe2x80x9cheadless chickenxe2x80x9d flapping. The apparatus involves the use of relatively low voltages, which consistently produce the desired currents.
The apparatus preferably further comprises a conveyor for conveying restrained poultry to the said stunning and slaughter devices. Most practical commercial slaughter operations, employ an automated moving production line.
The apparatus also preferably comprises a device for locating the bird""s head and/or neck to facilitate operation of the first device (stunning device. This may take the form of an elongate track running substantially parallel to the conveyor and spaced from it, the track comprising first and second track elements defining between them a space dimensioned to allow the bird""s neck but not its head to pass between the elements. Alternatively, the locating device may comprise a member arranged to move upwardly for engagement with the bird""s breast and/or neck. In this case, when the locating device is applied at an appropriate point in the conveyor path, the bird""s head and/or neck may be sandwiched between the locating device and an electrode or electrodes. One or both of the locating device and electrode(s) may move with the conveyor until a voltage has been applied to the bird""s head for a specified period of time.
Preferably, the electrical stunning device includes two head electrodes for engagement with the bird""s head, and the second device (the killing device) includes a body electrode for engagement with the rear of the bird""s body. In this case, the apparatus may further include electrical circuitry for applying a first voltage across the said head electrodes for a first predetermined time and for supplying a second voltage between the said body electrode and a further electrode(s) for a second predetermined time.
The body electrode may take the form of an electrode which moves into place against the rear of the bird""s body e.g. at its cloaca, at an appropriate point along the conveyor path.
In the current design, the said first predetermined time has elapsed before the application of the said second voltage commences, and there may be a short time delay between terminating application of the first voltage and commencing application of the second voltage. The said further electrode(s) may comprise one or both of the head electrodes. In this way, the second voltage is applied through the body and head of the bird.
The following compositions and/or constructions of electrodes are preferable:
(a) a resilient pad with an outer conductive layer;
(b) a resilient body through which pass substantially parallel elongate conductive members;
(c) an array of substantially parallel elongate conductive members movable against a resilient biassing force.
Alternatively, one or more of the electrodes may be in the form of a movable endless belt arranged to make contact with a bird as it moves along the conveyor. In this case, making the belt of a material with unidirectional conductivity may be advantageous. An example of such a material is that described above, comprising a resilient body with parallel conductive xe2x80x9cpinsxe2x80x9d passing through it.
Another possibility is for one or more of the electrodes to be in the form of an elongate bar arranged to make sliding contact with a bird as it moves along the said conveyor. In this case it may be advantageous to divide the electrode into electrically separated segments; provided only one bird is in contact with any one segment of the bar at any one time, making it relatively simple to ensure that the current flowing through the bird is constant.
The first aspect of the invention also embraces a method of slaughtering poultry comprising:
(a) restraining a bird;
(b) inducing an electrical current through the bird""s head and/or neck sufficient to stun the bird;
(c) simultaneously or subsequently applying an electrical voltage between the bird""s head and/or neck and its rear, preferably its cloaca, thereby, inducing through the bird""s heart an electrical current sufficient to kill it.
Optional method steps corresponding to the use of the apparatus features discussed above are also envisaged.
Fibrillation and hence killing of broiler chickens is preferably achieved by passing a current of 50 to 500 mA through the bird between a head and/or neck electrode and an electrode at the rear of the bird, preferably in contact with the cloaca. The current is more preferably 50 to 200 mA, 80 to 180 mA or 100 to 150 mA.
According to a second aspect of the present invention, a system for stunning and/or killing animals by applying an electric current includes:
(a) a conveyor for conveying the animal;
(b) a device for restraining the animal such that its head and/or neck is substantially immobilised with respect to the conveyor;
(c) a device for automatically applying an electric voltage across only the head and/or neck of the animal as it moves along on the conveyor, wherein the said electric voltage applying device comprise one or more of the following:
(i) an electrode adapted to make sliding contact with the animal""s head as the animal moves along the conveyor;
(ii) an electrode movable substantially in synchronism with the conveyor over at least a portion of its travel;
(iii) an electrode rail extending substantially continuously in the direction of travel of the conveyor and divided into electrically separated segments;
(iv) a conductive endless belt, optionally in sliding contact with a segmented electrode as in (iii) above;
(v) individual electrodes arranged to come into registry with and engage each side of the animal""s head and then to travel along in synchronism with the conveyor for a given time or length of travel and then to disengage with the animal""s head;
(vi) an electrode pair assembly with a xe2x80x9cVxe2x80x9d shaped recess for receiving an animal""s head.
There are two principal advantages of a system according to the second aspect of the invention. Firstly, the voltage required to achieve a stun or kill of an animal when applied to the head only is considerably lower compared with the water bath method. Secondly, with regard to poultry systems in particular, the resistance is more predictable when a water bath is not employed since the presence of water tends to create random additional electrical paths along parts of the surface of the bird which have been wetted.
In one possible arrangement, at least part of the voltage applying means is substantially stationary in the direction of movement of the conveying means and is arranged to make sliding contact with the animal""s head as the animal moves along. The advantage of this arrangement is that it is not necessary to provide moving electrified components. For example, the animal""s head could pass between two elongate electrified members so that sliding contact is made with each side of its head.
In an alternative arrangement, at least part of the voltage applying means is arranged to be moveable substantially in synchronism with the conveying means over at least a portion of the length of the conveying means.
If the electrodes are moveable, it is easier to make good contact with the animal""s head, but this obviously increases the complexity of the system somewhat.
In either of the above cases, the voltage applying means may include an elongate electrode rail extending substantially continuously in the direction of travel of the conveying means and divided into electrically separated segments.
In this way, it is possible to ensure that a constant current is passed through any individual animal passing along the electrode even if there are a number of animals in contact with the electrode, by ensuring that only one animal makes contact with any one segment at any given time.
The voltage applying means may include a conductive endless belt. A belt is one of the simplest forms of moveable electrode.
Where a segmented electrode rail is used, as described above, it is possible to combine this with a conductive endless belt which is conductive of electricity only in a direction transverse to the direction of movement of the belt. The belt would preferably run across the surface of the segmented electrode rail, making electrical contact with it. Because of the unidirectional conductivity of the belt, only that portion of the belt in contact with an animal""s head will conduct electricity from the segmented rail.
In this way, it is possible to combine the advantages of a moving electrode with the advantages of an arrangement where sliding contact is made with a static rail.
A further possible arrangement would be an electrode conveyor system, e.g. comprising an endless belt on which is mounted a number of discrete electrodes for contacting the animals. Such a system might have a belt on each side, with discrete electrodes moving around the respective belts in synchronism. In such a system, it would be desirable automatically to sense the arrival of an animal and guide the electrodes into contact with the animal as it moves along the conveyor. It may therefore be desirable to have some form of stacking system for the electrodes and an arrangement whereby they are picked up by some form of latching means on the endless belt or belts at an appropriate time.
In one possible arrangement, the electrodes have a xe2x80x9cVxe2x80x9d shaped recess for receiving the head of the animal. This provides good contact with the head, particularly if a degree of force is maintained between the electrode and the animal""s head. In one arrangement, corresponding electrodes on each side of the track meet immediately prior to engaging with the animal""s head and together form a xe2x80x9cVxe2x80x9d shaped recess.
Of course, with the above described arrangements employing individual electrodes, it is not necessary for electrodes to be mounted on a belt. In general, the voltage applying means may include individual electrodes arranged to come into registry with and engage each side of the animal""s head for a given length of time or length of travel and then travel along on some conveying means which may or may not be part of the conveyor for conveying the animal, and then to disengage the animal""s head after the said given time or length of travel.
According to a third aspect of the present invention, apparatus for electrically stunning and/or killing animals includes one or more electrodes of sufficiently resiliently deformable construction to conform to a degree to the shape of the contacted part of the animal. Although electrodes comprising a spongy material soaked in an electrolyte (eg brine) are known, there are problems involved with using a wet electrode, including the danger of surplus electrolyte creating unwanted paths for conduction of electricity and the possibility of the electrodes drying out fully or partially. It is therefore envisaged that the electrode will be dry and will conduct electricity by virtue of the materials from which it is constructed.
Using an electrode in accordance with the invention, the contact area with the animal is maximised without the application of undue pressure. Sufficient pressure to deform the electrodes to the shape of the appropriate part of the animal without causing undue discomfort to the animal is all that is required.
Preferably, the electrode is compressible. If the electrode is not only deformable but compressible, it is easier to apply an even force over the whole area of the electrode to ensure good contact.
In one arrangement, the electrode comprises conductive compressible material, for example a conductive foam of some sort. In an alternative arrangement, a non-conductive compressible material has a deformable surface layer, film or mesh of conductive material.
Another possibility is for the electrode to comprise an array of parallel elongate conductive members (pins) arranged so as to be movable against a resilient biassing force. For example, an array of pins with their ends defining between them a plane could be arranged such that the pins can be pressed xe2x80x9cinwardlyxe2x80x9d, ie out of the plane against a spring of some sort. This amounts to providing a resiliently deformable surface for the electrode.
In some applications it is preferable for the electrodes to have unidirectional conductivity. This may be the case, for example, in an automated system where the electrodes take the form of endless belts which the animal""s head comes into contact with. In this case the belt electrodes may slide along a static conductor rail on one side of the belt, whilst the animals"" heads come into contact with the opposite side of the belt. It may be desirable in this case for current not to be conducted around the entire belt.
One type of material having unidirectional properties comprises a compressible non-conductive material in which is embedded substantially parallel conductors, e.g. wires. A similar material could be envisaged which has conventional non-directional conductivity, comprising a resilient material with thin metal strands randomly distributed throughout it.
Electrodes as described above may also of course be useful in manual stunning and killing apparatus, which normally takes the form of a pair of tongs with electrodes at the ends.
According to a fourth aspect of the invention animal handling apparatus for locating an animal""s head and/or neck comprises:
(a) an elongate track comprising first and second track elements defining between them a space dimensioned to allow the animal""s neck but not its head to pass between the elements;
(b) animal conveying means spaced from the track and running substantially parallel to it.
It is preferred that the conveyor be arranged to convey the animal in a non-inverted position. As the animal (e.g. broiler chicken) travels along the conveyor, its neck is positioned in the track and its head/neck thereby immobilised to a degree. This may facilitate the performance of some other operation on its head/neck, e.g. the application of electrodes for a stun/kill operation.
Of course, there are many other possibilities for different uses of this apparatus. For example, with its head located in this way, the animal""s head could be subjected to some kind of automatic monitoring process, or have some kind of treatment applied to it.
Preferably, means are provided for increasing or decreasing the spacing between the tracks and supporting means. This is preferably done in response to the sensed size, shape, orientation, position or attitude of the animal or of its head/neck.
It will be appreciated that the animal may be in a variety of orientations, positions or attitudes on the conveyor depending in part on the nature of the conveyor (although as stated above, it is preferred that the animal is not inverted), and also that it is desirable that animals of different size and shape be accommodated. These parameters may be sensed, either prior to the animal entering or as it enters or as it passes along the track, the spacing between the track and conveyor may be adjusted accordingly. In this way it may be possible to ensure that the animals"" neck is correctly introduced into the track and/or that its head/neck are correctly positioned with respect to its body subsequent to introduction, and/or that it adopts a desired body position or attitude. For example, a broiler chicken whose neck is engaged in the track might have its head lifted to a desired height by raising the track, and/or might be encouraged to stand instead of sit on a conveyor.
It may also be desirable to provide means for moving the track transversely with respect to the conveyor in dependence on the above sensed parameters.
The entry portion of the track is desirably flared to assist entry of the animals"" neck.
In one possible embodiment, the track or part of it (e.g. the entry portion) itself comprises a moveable belt or similar, which may move in synchronism with the main conveying means. This may have the advantage of facilitating the birds"" passage through the system and reducing friction between the birds and the track.
One possible method of automatically adjusting the spacing between the track and conveyor is for the flared entry portion to engage with the body of the animal as it enters. This arrangement is appropriate for a system where the track is above the conveyor, although the invention is not limited to this case. The track may be supported so as to be movable generally vertically; when an animal engages with the flared entry portion of the track, the track is moved upwards until the track is aligned with the animal""s neck. In this way, at least the size of the broilers is xe2x80x9csensedxe2x80x9d and the track lifted automatically in dependence on the xe2x80x9csensedxe2x80x9d size. This particular system will be more suited to some animals than others, but has been found to work well with broilers which are oriented with their backs towards the track as they approach on the conveyor, and which are already constrained to adopt a standing position.
Desirably, in the system described above, the flared entry portion of the track is also angled away from the conveyor, so that the initial contact with the animal, e.g. with the broiler""s back, is gentle and the relative movement between the animal and track tends to gradually raise the track until it is level with the animals"" neck.
Alternatively, the majority of the track may be at a fixed height and the flared entry portion pivotally mounted to the remainder of the track. A further alternative might be for the entire track to be mounted pivotally.
These two options of course have the advantage that a hinged mounting is much simpler than a mounting which allows the track to move vertically whilst remaining horizontal.
It is envisaged that other methods could be used for aligning the entry portion of the track or for adjusting the position of the track once the animal""s neck is located within it. For example, electronic sensors could detect the size, shape, position, orientation and/or attitude of the animal and movement of the track or parts thereof automatically controlled according to the output from the sensor(s).
In a preferred embodiment of the invention, the conveying means comprises means for restraining the body and/or legs of the animal. In this way, the position, orientation and/or attitude of the animal is determined to a greater extent than it would be if the animal were simply sitting or standing on a conventional horizontal conveyor belt. The design of the track, and in particular those features of the track and its mounting concerned with the introduction of the neck of the animal into the track, is thereby simplified. The design of any automatic track adjustment system employing sensors would also thereby be simplified.
The apparatus may form a part of a system for stunning and/or killing animals, in which case a portion of the track may be electrified and/or the track may have electrodes mounted thereon.
It will be appreciated that the fourth aspect of the invention could be used in conjunction with a suspended bird shackle line, in which case the track would be beneath the conveyor.
It will also be appreciated that many of the concepts described in connection with each of the four aspects could be used in combination since the four aspects of the invention are all very closely related.